In refractive opthalmological surgery, the refractive properties of a patient's eye are modified by interventions on the eye in order to correct defective vision. In particular the so-called LASIK method (LASer In Situ Keratomileusis) is known, in which the patient's cornea is reshaped. According to the conventional LASIK method, a flat corneal incision is made in a first microsurgical operation step with a mechanical instrument, usually a microkeratome. This creates a so-called “flap”, which can be folded away so that underlying corneal tissue (stroma) is exposed. In the subsequent part of the LASIK operation, a particular ablation pattern is removed from the stroma. The flap is then folded back into place and heals relatively rapidly again with the remaining stroma. The conventional mechanical microkeratome uses a sharp, rapidly oscillating blade.
Recently, the microkeratome has been replaced by a laser, in particular a femtosecond laser, which makes the aforementioned flat incision in the cornea. The laser is focused onto a plane below the surface of the cornea, and is guided on a path which produces the flap in the same way as the microkeratome does. The extremely short laser pulses used for this, in the femtosecond range, have such high powers that, with a suitable focusing, it is possible to cut without causing internal heating effects or the like by utilising the so-called photodisruptive effect. Compared with the conventional mechanical microkeratome, higher accuracy and better reproducibility of the LASIK cuts are generally obtained.
In order to produce the flap by means of a laser, the patient is first positioned below the femtosecond laser. As for the conventional production of a flap by means of a microkeratome, a fixation ring, which is usually fixed by means of suction, is placed onto the eye. A contact glass, which touches the surface of the cornea and flattens it for maximally accurate production of the corneal incision by exerting a certain pressure, is then placed into the suction ring. A usually conical contact device is then connected to the actual femtosecond laser instrument. This is usually done so that the part of the laser instrument, which emits the laser radiation, is moved with the aid of a motor into the conical contact device. At this time, the patient's eye is already fixed and stressed by the suction ring and the contact glass in a way which is uncomfortable for the patient. The process of making contact between the suction ring and the laser instrument further increases the stress for the patient, since the process is usually not accomplished entirely smoothly. An additional pressure is therefore exerted at least briefly on the patient's eye, which can be physiologically and psychologically detrimental for the patient.
It is therefore an object of the present invention to provide a remedy in respect of this stress.